Interlock device for auxiliary counting circuit in reproduction apparatus

ABSTRACT

Disclosed is an interlock device for an auxiliary copy-counting circuit in a reproduction apparatus having a movable cover for an original to be copied. The device includes a signal generator, at least one pair of induction coils in both the body and in the movable cover of the apparatus, each coil in the cover being located to form a transformer with a correspondingly located coil in the body of the apparatus when the cover is in the closed position over an original, whereby at least two transformers are formed. The primary coil of one of the transformers is preferably located in the body of the apparatus and is connected to the signal generator, whereas the secondary coil of this same transformer is located in the cover and is connected with the primary coil, also located in the cover of the other transformer. The secondary coil of this latter transformer is then located in the body and is connected to a control means which is responsive to the transmitted signal and actuates the auxiliary counting circuit. The device may also include additional pairs of transformers in the foregoing sequence.

United States Patent [191 Moser et al.

[ INTERLOCK DEVICE FOR AUXILIARY COUNTING CIRCUIT IN REPRODUCTION APPARATUS [75] Inventors: Hermann Moser, Darmstadt; Walter Pils, Bremthal, both of Germany [73] Assignee: Hoechst Aktiengesellschaft,

Frankfurt am Main, Germany 22 Filed: on. 9, 1973 211 Appl. No.: 404,785

[30] Foreign Application Priority Data Oct. 9, 1972 Germany 2249408 [52] US. Cl. 307/116; 335/75 [5 l] Int. Cl. II0ll1 36/00 [58] Field of Search 307/116, H7, 118, 119; 355/l33, 75, l4, 8, 11, 120, 13; 317/DIG. 2;

200/1; 235/92 NT, 92 PC, 92 SB; 340/274 [56] References Cited UNITED STATES PATENTS 2,967,267 1/l96l Steinman et al, 336/DIG. 2 3,020,473 211962 Cauley 235/92 SB 3,533,691 10/1970 Suzuki et al. 355/!3 51 May 20, 1975 Primary Examiner-Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorney, Agent, or Firm-Richard L. Schwaab 5 7 ABSTRACT Disclosed is an interlock device for an auxiliary copycounting circuit in a reproduction apparatus having a movable cover for an original to be copied. The device includes a signal generator. at least one pair of induction coils in both the body and in the movable cover of the apparatus, each coil in the cover being located to form a transformer with a correspondingly located coil in the body of the apparatus when the cover is in the closed position over an original, whereby at least two transformers are formed. The primary coil of one of the transformers is preferably located in the body of the apparatus and is connected to the signal generator, whereas the secondary coil of this same transformer is located in the cover and is connected with the primary coil, also located in the cover of the other transformer. The secondary coil of this latter transformer is then located in the body and is connected to a control means which is responsive to the transmitted signal and actuates the auxiliary counting circuit. The device may also include additional pairs of transformers in the foregoing sequence 13 Claims, 4 Drawing Figures AUXILIARY COUNTER ZG PATENTED HAYZU I975 SHEEI 10F 3 PATENTEB HAY 2 01975 SHEET 3 BF 3 INTERLOCK DEVICE FOR AUXILIARY COUNTING CIRCUIT IN REPRODUCTION APPARATUS BACKGROUND OF THE INVENTION The present invention relates to an electrical interlock device for a circuit, and more especially to an interlock device for an auxiliary copy counting circuit in a reproduction apparatus.

In the field of copying technology today, it is a widespread practice to provide counting mechanisms which, in the case of multiple copying of a single original, allow calculation of the copying price on a sliding scale. Thus, for example, counting mechanisms may be used which, in the case of multiple copies, count only the copies from l to 5 with a first counter and count further copies, from 6 to for example, with a second counter.

Various devices have already been proposed to prevent the price reduction afforded for multiple copying from being utilized for single copies of different originals, which may occur when the individual originals are quickly changed during the short pauses between stages of the copying cycle of the apparatus, although the copying apparatus continues to run as if for the production of multiple copies. The simplest device of this type comprises a mechanical switch which is actuated by a cover mat for covering the original to be copied. In addition, a device has been proposed in which a magnet is arranged in the cover mat and actuates a switch situated in the copying apparatus. Finally, inductive approach switches have been proposed in which a metal insert in the cover initiates a switching function when it approaches a switching circuit in the apparatus.

All of these interlock devices suffer from the considerable disadvantages that they may very simply be brought into a state corresponding to that in which a cover plate lies on an original, irrespective of whether the cover plate is in fact in position. It is thus possible, using the previously proposed devices, to produce single copies of different originals with the cover plate removed, while the interlock device has switched in the special reduced price counting circuit. In the case of the mechanical switch, this can be done by actuating the switch with the hand or by means of a suitable, simple aid, for example, a strip of adhesive tape. In the case of a magnetically operated switch, the counting device can be kept in the switched-on state by the application of a permanent magnet to the correct location on the apparatus, and, in the case of an inductive approach switch, the auxiliary counter may be actuated by the application ofa metal plate. In both instances it is not necessary for the cover plate to be closed.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an interlock device for an auxiliary cope counting circuit in a reproduction apparatus which effectively switches on the auxiliary copy counting device when the cover is in the closed position over an original for multiple copying, but which likewise prevents the registration of multiple copies upon the auxiliary counter when the cover is not in fact in the closed posi tion.

It is also an object of the present invention to provide an interlock device for an auxiliary copy counting circuit in a reproduction apparatus which is extremely reliable yet which is sufficiently sophisticated that a simu lation of the condition in which the cover is closed is not readily perceivable or capable of accomplishment by the average operator of the apparatus.

A further object of the invention resides in the provision of an interlock device for an auxiliary copy counting circuit in a reproduction apparatus which renders it virtually impossible to artificially duplicate the condition for switching on the auxiliary counting circuit when the cover is placed over an original.

It is yet another object of the present invention to provide a reproduction apparatus which embodies an interlock device for an auxiliary copy counting circuit having the advantages set forth in the foregoing objects of the invention.

In accomplishing these and other objects, there has been provided in accordance with the present invention an interlock device for an auxiliary copy-counting circuit in a reproduction apparatus having a body and a movable cover for an original to be copied, this de vice comprising an electrical signal generator. preferably an oscillator, at least one pair of induction coils in both the body and in the cover of the apparatus, each coil of each pair in the cover being located to form a transformer with a correspondingly located coil of each pair in the body when the cover is in the closed position over an original, whereby there is formed at least a first and second transformer each having a primary and secondary coil, means for coupling the primary coil of the first transformer with the signal of the signal generator, means for coupling the signal from the secondary coil of the first transformer with the primary coil of the second transformer, and control means electrically coupled with the secondary coil of the second transformer and being responsive to the signal thereof to actuate the auxiliary counting circuit. Preferably, the primary coil of the first transformer and the secondary coil of the second transformer are both located in the body of the apparatus. An amplifier is typically introduced following the oscillator, and the control preferably comprises a receiver, for example, an amplifier in combina tion with a frequency filter, and a suitable switching mechanism, such as a relay in combination with a rectifier. Alternatively, there may be employed one or more additional pairs of transformers between the aforementioned first and second transformers, and in the case of a single additional pair, one of these additional transformers has its primary coil connected to the secondary coil of the first transformer and has its secondary coil connected with the primary coil of the second additional transformer. The secondary coil of this second additional transformer is then connected to the primary coil of the aforementioned second transformer which actuates the switching mechanism which in turn actuates the auxiliary counting circuit. Most preferably, the

respective primary and secondary coil of the additional transformers are arranged one each in the cover and body portions of the apparatus in the same manner as with the first and second transformers.

There is also provided in accordance with the present invention a reproduction apparatus for preparing copies of an original image, including a supporting surface for the original image, a portion of which surface is scanned during the copymaking process, a cover member movably adapted to be placed over the original image, an auxiliary circuit for counting multiple copies of a single image and interlock means for actuating the auxiliary counting circuit when the cover member is in the closed position over the original image, the improvement in this apparatus comprising the use therein of an interlock device as described in the immediately foregoing paragraph. In such an apparatus, one edge of the cover member is connected to the body of the apparatus, preferably in a hinged fashion, and the induction coils in the cover are positioned in the region of one of the other, non-connected edges of the cover. Most preferably, in the case where there is only a single pair of induction coils in both the cover and the body of the apparatus, the transformers defined by each cor responding pair of coils when the cover is in the closed position are located on opposite sides of the scanned area of the supporting surface.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of the invention which is to be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a diagrammatic perspective view of a copy ing apparatus illustrating the support surface for the originals being copied and the cover for the support surface;

FIG. 2 is a block wiring diagram for an interlock device according to the invention;

FIG. 3 is an enlarged view of the transformers used in accordance with the invention; and

FIG. 4 shows a further embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a copying apparatus wherein a cover for an original to be copied includes at least one pair of induction coils, the coils in each individual pair being electrically or inductively coupled together and the coils being so arranged that, when the cover is in position over the original, each coil together with a corresponding coil in the body of the apparatus forms a transformer, such that a switch-actuating se quence is completed, this sequence being such that it can be broken by removing the cover from the original.

In the copying apparatus of the invention, the cover may include one pair of induction coils, one of which forms the secondary coil of a first transformer when the cover is in position and the other of which forms the primary coil of a second transformer. Alternatively, the cover may include a plurality of pairs of induction coils, in which case the body of the apparatus contains an equal number of pairs of coils, the coils in each adjacent pair of coils in the body of the apparatus being electrically connected together, and the coils being so arranged that, when the cover is in the closed position, they form a series of transformers. In this series an electrical signal received at the first coil of the first trans former, which first coil is preferably situated in the body of the apparatus, can pass by induction to the secondary coil of the first transformer, by conduction from that secondary coil to the primary coil of the next transformer, and so on until it reaches the secondary coil of the last transformer, which secondary coil too is preferably situated in the body of the apparatus. Optionally, both coils of any transformers intermediate the first and last transformers could be located solely in the cover member.

The auxiliary counting circuit actuating device of the invention preferably includes a generator for delivering an electrical voltage at a particular frequency, the output of the generator being electrically connected to the primary coil of the first transformer, and a receiver which is tuned to the same frequency as the generator and can close a switch on receiving a sufficiently strong signal of this frequency The input of the receiver is connected to the secondary coil of the second or the last transformer, as the case may be.

The apparatus of the invention, therefore, no longer suffers from the disadvantages mentioned above. i.e., the interlock cannot be kept in the switched-on state by any simple means when the cover is not actually closed.

In a preferred embodiment of the invention, the security device is characterized by the fact that the copying apparatus includes a generator which delivers an electrical voltage of a particular frequency, and also a receiver which is tuned to the same frequency and which switches the counting circuit on upon receiving a sufficiently strong signal at this frequency. The output of the generator is connected to the primary coil of a first transformer which is arranged in the copying apparatus in the vicinity of some portion of the cover when the latter is in the closed position, and the second coil of the first transformer is so arranged in the cover that, when the cover is closed, the coil is in the vicinity of the aforementioned primary coil. The primary coil of a further or second transformer is then arranged at a distance from the secondary coil of the first transformer, also in the cover, and is wired to the latter to form a closed circuit. The secondary coil of the second transformer is arranged in the copying apparatus at a point which lies in the vicinity of the primary coil of this transformer when the cover is closed. and this secondary coil is connected to the input of the receiver, which is so constructed and arranged that upon receiv ing a sufficiently strong signal, the special counting de vice circuit is switched on, Further pairs of transformers, one coil of which is arranged in the cover in each case and the other coil in the copying apparatus, at points adjacent to the position of the associated coil when the cover is closed, may be positioned between the first and second transformers and appropriately connected to conduct the signal.

In order to bypass the interlock device of the invention it is necessary to connect two induction coils with one another to form a closed electrical circuit and in each case to arrange this exactly at the point where the corresponding coils of the two transformers are arranged in the copying apparatus. This procedure requires such a great degree of knowledge and skill that it can be assumed that bypassing of this device is substantially excluded. The interlock device is also simply constructed, it can be provided in any copying apparatus at no great cost, and it can easily be fitted subsequently into any existing copying apparatus. In particular, no electrical connections pass from the cover plate into the copying apparatus so that the likelihood of failures or faults occurring is extremely slight. The device is also suitable for use in virtually any type of reproduction apparatus which employs a movable cover for original documents, e.g., electrostatic copies, electrophotographic copiers, photographic copies, and the like.

Referring now to the drawings. FIG. I shows part of a housing cover plate I of a copying apparatus operating, for example, on an electrophotographic basis. An

original 3 may be placed on a transparent original support surface 2; this original can be reproduced many times in the copying apparatus (which is not shown in detail). The original 3 positioned on the transparent plate 2 is covered by a cover 4 during a multiple copying operation.

The cover 4 may be a flexible or a rigid cover. and it has on its upper side a handle 5. In the cover 4 there are two flat coils 6 and 7 which are connected to one another to form a closed electrical circuit. The coils are so arranged that the voltage induced in the coil 6 produces a current in the coil 7. The coils 6 and 7, together with their connections, are completely embedded in the non-metallic material of the cover 4, and are in an area of the cover 4 which lies outside the area covering the glass plate 2, i.e., outside the scanned area. The coil 7 represents the secondary coil of a first transformer, and the coil 6 is the primary coil of a second transformer. When the cover 4 is in the closed state, two further coils, 8 and 9, which are in the vicinity of the surface of the plate 1 are positioned exactly below the coils 6 and 7. When the cover is closed, therefore, the coils 6 and 8 and the coils 7 and 9, respectively, are exactly one above the other. The coils 8 and 9 are so arranged in the cover plate 1 that they cannot be seen from outside. Because of the invisible arrangement of the coils, the bypassing of the interlock device is rendered even more difficult.

All of the coils 6, 7, 8 and 9 are flat coils. The coils 6 and 7 in the cover plate are preferably somewhat larger in diameter than the coils 8 and 9 in the apparatus in order to ensure perfect operation of the device even with slight deviations in the position of the coils arising from manufacturing. Metal parts between the coils 7 and 9 and coils 6 and 8 should be avoided to the extent possible in order to avoid transfer of the alternating voltage by means of eddy currents.

The method of operation of the device will now be explained with reference to FIGS. 2 and 3. Each pair of coils, 6 and 8 as well as 7 and 9, forms a transformer 12 or 13. The coil 9 forms the primary coil of the transformer l3, and the coil 8 forms the secondary coil of the transformer 12. In a corresponding manner, the coil 7 forms the secondary coil of the transformer 13, and the coil 6 defines the primary coil of the transformer 12. The coils 9 and 8 of the two transformers are connected to an electrical control unit which includes a generator 14 and a receiver 15.

The generator 14 comprises an oscillator 141 and an amplifier 142. The receiver 15 comprises an amplifier 151 and a frequency filter 152. A rectifier 16 and a relay 17 are connected after the frequency filter 152 and form a control element for the auxiliary counting circuit 25. The relay l7 switches the auxiliary multiple copy counter 26 of the copying apparatus on or off by way of the leads l8 and 19.

When the cover 4 is in the closed position, the method of operation of the circuitry is as follows: The oscillator 141 delivers to the primary coil 9 of the first transformer 13 a voltage of a particular frequency, the voltage being amplified by means of the amplifier 142. Since the cover plate is closed, a voltage of the oscillator frequency is also produced at the secondary coil 7 of the first transformer 13. Wired together with the coil 7 is the primary coil 6 of the second transformer 12, to which the same voltage with the same frequency is therefore applied. From this primary coil 6 of the sec- 0nd transformer 12, the alternating voltage is transmitted to the secondary coil 8. The coils 6 and 8 and the coils 7 and 9, respectively, are relatively close to one another in view of the fact that the cover 4 is closed. The voltage induced in the secondary coil 8 is amplified by means of the amplifier 151 and is filtered by means of the frequency filter 152. The frequency filter 152 is so adjusted that it allows the frequency of the oscillator 141 to pass through it. Thus, when the cover is closed, a voltage rectified by means of the rectifier 16 reaches the relay 17. The relay 17 is excited and switches on the special counting circuit 25, and hence, the counting device 26. The frequency may be selected either by means of a wide band oscillating circuit or by means of selective amplifiers, for example operational amplifiers with corresponding input and feedback circuit arrangement, the details thereof being familiar to the artisan.

When the cover 4 is open, however, the following occurs: Because of the considerable distance between the primary coil 9 and the secondary coil 7 of the first transformer and the considerable distance between the primary coil 6 and the secondary coil 8 of the second transformer, the alternating voltage signal delivered by the generator 14 can no longer be transmitted from the primary coil 9 to the secondary coil 8. A sufficiently strong signal, therefore, no longer reaches the rectifier 16 by way of the amplifier 151 and the frequency filter 152. The relay 17 is thus in the non-excited state and the leads 18 and 19 are separated, so that the auxiliary counting circuit 25 is no longer switched on.

The following test is carried out using the device of FIGS. 1 to 3:

An oscillator is used which produces an alternating voltage of 25 kHz. The signal amplified in the amplifier 142 could, when the cover is closed, be amplified in the amplifier 151, filtered in the frequency filter 152, rectified in the recitfier 16 and, after being amplified once more, could be used to trigger a relay. When the cover 4 is raised, the relay 17 no longer responds. This interlock device thus makes it possible to completely exclude any simple bypassing thereof by means of metals or magnetic effects.

Instead of two transformers, addition pairs, e.g, four or six etc., may be used. In this case the secondary coil of the transformer adjacent the first transformer is wired together with the primary coil of the next transformer and the circuitry described above is repeated. An example of a device with four transformers 12, 13, 20, 21 is shown in FIG. 4. The signal from the generator 14 only reaches the receiver 15 when the cover 4 is closed.

Thus, there has been provided in accordance with the present invention an interlock device for an auxiliary counting circuit in a copying apparatus which is both dependable and also nearly incapable of being bypassed. While this interlock device has been described with reference to several specific embodiments thereof, it will be apparent that many modifications, additions and the like may be made thereto without departing from the spirit of the invention. Therefore, it is understood that the scope of protection will be determined solely by the appended claims.

What is claimed is:

1. An interlock assembly for an auxiliary copycounting circuit in a reproduction apparatus having a body and a movable cover for an original to be copied, comprising means to generate an electrical signal, at

least one pair of induction coils on the body of the apparatus, at least one pair of induction coils on the cover of the apparatus, each coil of each pair on the cover being located over the position of a corresponding coil of each pair on the body to thereby form at least a first and a second transformer when the cover is closed over the original, each of said transformers having a primary and secondary coil, means for coupling the primary coil of said first transformer with said signal generating means, means for coupling the secondary coil of said first transformer with the primary coil of the second transformer, and control means electrically coupled with the secondary coil of the second transformer to control an auxiliary counting circuit in response to said signal from said signal generating means being coupled through said first and second transformers, whereby said control means is disabled when the cover is opened.

2. The interlock assembly as defined by claim 1, wherein the primary coil of the first transformer and the secondary coil of the second transformer are both located in the body of the apparatus.

3. The interlock assembly as defined by claim 1, wherein the signal generating means comprises an oscillator.

4. The interlock assembly as defined by claim 3, wherein the signal generating means further comprises an amplifier following said oscillator.

5. The interlock assembly as defined by claim 1, wherein the control means comprises a means for receiving the signal from said secondary coil and switching means electrically coupled with said receiving means for actuating the auxiliary counting circuit.

6. The interlock assembly as defined by claim 5, wherein said receiving means comprises an amplifier and a frequency filter following said amplifier.

7. The interlock assembly as defined by claim 5, wherein said switching means comprises a rectifier and a relay following said rectifier.

8. The interlock assembly as defined by claim 1, wherein said means for coupling the secondary coil of the first transformer with the primary coil of the second transformer comprise at least one additional pair of transformers including a third and fourth transformer each having a primary and a secondary induction coil, the primary coil of said third transformer being electrically connected to the secondary coil of said first transformer, the secondary coil of said fourth transformer being electrically connected with the primary coil of said second transformer, and means for coupling the secondary coil of said third transformer with the primary coil of said fourth transformer.

9. The interlock assembly as defined by claim 8, wherein at least said third and fourth transformers each comprises a pair of induction coils, one of which is located in the cover of the apparatus and the other of which is positioned in a corresponding location in the body of the apparatus when the cover is in the closed position.

10. The interlock assembly as defined by claim 9, wherein the primary coils of the first and fourth transformers and the secondary coils of the second and third transformers and the secondary coils of the second and third transformers are located in the body of the apparatus and the corresponding coils of each of the first through fourth transformers are located in the cover of the apparatus.

11. In a redproduction apparatus for preparing copies of an original image, including a supporting surface for the original image, a portion of which surface is scanned during the copy-making process, a cover member movably adapted to be placed over the original image, an auxiliary circuit for counting multiple copies of a single image and interlock means for actuating said auxiliary counting circuit when the cover member is in the closed position over the original image, the improvement comprising said interlock means being the interlock assembly according to claim 1, with the body and the cover thereof, comprising, respectively, the supporting surface and the cover member of the apparatus.

12. A reproduction apparatus as defined in claim 11, wherein one edge of the cover member is connected to the body of the apparatus and the induction coils in said cover are positioned in the region of one of the non-connected edges of the cover.

13. A reproduction apparatus as defined by claim 12, wherein the first and second transformers are defined in the closed position of the cover member on opposite sides of the scanned area of said supporting surface.

l l i 

1. An interlock assembly for an auxiliary copy-counting circuit in a reproduction apparatus having a body and a movable cover for an original to be copied, comprising means to generate an electrical signal, at least one pair of induction coils on the body of the apparatus, at least one pair of induction coils on the cover of the apparatus, each coil of each pair on the cover being located over the position of a corresponding coil of each pair on the body to thereby form at least a first and a second transformer when the cover is closed over the original, each of said transformers having a primary and secondary coil, means for coupling the primary coil of said first transformer with said signal generating means, means for coupling the secondary coil of said first transformer with the primary coil of the second transformer, and control means electrically coupled with the secondary coil of the second transformer to control an auxiliary counting circuit in response to said signal from said signal generating means being coupled through said first and second transformers, whereby said control means is disabled when the cover is opened.
 2. The interlock assembly as defined by claim 1, wherein the primary coil of the first transformer and the secondary coil of the second transformer are both located in the body of the apparatus.
 3. The interlock assembly as defined by claim 1, wherein the signal generating means comprises an oscillator.
 4. The interlock assembly as defined by claim 3, wherein the signal generating means further comprises an amplifier following Said oscillator.
 5. The interlock assembly as defined by claim 1, wherein the control means comprises a means for receiving the signal from said secondary coil and switching means electrically coupled with said receiving means for actuating the auxiliary counting circuit.
 6. The interlock assembly as defined by claim 5, wherein said receiving means comprises an amplifier and a frequency filter following said amplifier.
 7. The interlock assembly as defined by claim 5, wherein said switching means comprises a rectifier and a relay following said rectifier.
 8. The interlock assembly as defined by claim 1, wherein said means for coupling the secondary coil of the first transformer with the primary coil of the second transformer comprise at least one additional pair of transformers including a third and fourth transformer each having a primary and a secondary induction coil, the primary coil of said third transformer being electrically connected to the secondary coil of said first transformer, the secondary coil of said fourth transformer being electrically connected with the primary coil of said second transformer, and means for coupling the secondary coil of said third transformer with the primary coil of said fourth transformer.
 9. The interlock assembly as defined by claim 8, wherein at least said third and fourth transformers each comprises a pair of induction coils, one of which is located in the cover of the apparatus and the other of which is positioned in a corresponding location in the body of the apparatus when the cover is in the closed position.
 10. The interlock assembly as defined by claim 9, wherein the primary coils of the first and fourth transformers and the secondary coils of the second and third transformers and the secondary coils of the second and third transformers are located in the body of the apparatus and the corresponding coils of each of the first through fourth transformers are located in the cover of the apparatus.
 11. In a redproduction apparatus for preparing copies of an original image, including a supporting surface for the original image, a portion of which surface is scanned during the copy-making process, a cover member movably adapted to be placed over the original image, an auxiliary circuit for counting multiple copies of a single image and interlock means for actuating said auxiliary counting circuit when the cover member is in the closed position over the original image, the improvement comprising said interlock means being the interlock assembly according to claim 1, with the body and the cover thereof, comprising, respectively, the supporting surface and the cover member of the apparatus.
 12. A reproduction apparatus as defined in claim 11, wherein one edge of the cover member is connected to the body of the apparatus and the induction coils in said cover are positioned in the region of one of the non-connected edges of the cover.
 13. A reproduction apparatus as defined by claim 12, wherein the first and second transformers are defined in the closed position of the cover member on opposite sides of the scanned area of said supporting surface. 